“The last push of sugar the tree pushes for preperation for winter is used to produce the next years crop of buds and it is this over abundance of sugar that makes the trees turn color. The better and more brilliant the Fall color, the better the crop of new buds for the next year. Those of you not getting good fall color are not growing healthy maples.”

It seems that I recieved a couple emails and a comment from Shane Martin in AUS.

Shane says:

“Hi Al,Early in this piece you said if you’re not getting good fall color, then you’re not growing healthy trees….. What are they lacking?I was always of the belief, that good fall color was due to low temperatures and shorter hours of sunlight?”

I Think I can answer this question with a blog post. First we have to determine why a maple turns red in the first place. It does this to keep the tree from losing its leaves in an effort to transfer energy from the leaves to the trunk and roots. How is this done?

For a large part of the year, leaves are a tree’s workhorses, constantly converting carbon dioxide, water and sunlight into energy in a process called photosynthesis. The special ingredient for this process, the pigment chlorophyll, is w­hat gives leaves their bright, green color for much of the year. But while chlorophyll is the star of the show, it has some help in the form of the pigments carotene and xanthophyll. Xantho is Greek for “yellow,” and carotene is what gives items like carrots and eggyolks their orangish color. These two pigments are always present in leaves and help absorb sunlight, which they transfer to chlorophyll for photosynthesis.

As summer nears its end and days get shorter, the increased amount of darkness incites trees to prepare for a sort of hibernation. Leaves won’t be able to continue photosynthesizing during winter due to the dry air and lack of sunlight , so the tree does two things. First, it forms a separation layer made of corklike cells at the base of each leaf to seal it off from the tree. Second, it stops producing chlorophyll since it won’t need this pigment until the days start to lengthen once again in the spring. With chlorophyll out of the picture, the yellow and orange pigments get a chance to shine.

The red hues, which come from pigments called anthocyanins, are slightly more complicated. Whereas all trees contain chlorophyll, carotene and xanthophyll, not all of them produce anthocyanins. Even the ones that do have anthocyanins only produce it under certain circumstances.

Remember that layer of cells at the base of the leaf? Its purpose is to protect the tree during the colder winter and prevent it from drying out. When the separation layer is complete, the leaves fall off in the tree’s attempt to conserve energy. But before the leaves fall off and the tree closes up shop, it wants to pull in as much sugar and nutrients as possible from its leaves, which is where the anthocyanin comes in.

Although scientists offer several different reasons for why some trees produce anthocyanins and autumn leaves change color, the prevailing theory is that anthocyanins protect the leaves from excess sunlight and enable the trees to recover any last remaining nutrients. The reason you’ll see more vibrant reds during some years is that lots of sunlight and dry weather increase the sugar concentration in tree sap, triggering the tree to release more anthocyanins in a last-ditch effort to gather up energy to get through the winter. In addition, near-freezing weather, low nutrient levels and other plant stressors seem to trigger increased levels of anthocyanins.

If it’s been especially rainy and overcast, you won’t see much red foliage. Without bright sunlight, the trees don’t need the added protection that the red pigments provide, so they don’t bother producing them.

What this means is that damaged leaves like wind burnt and sun burnt leaves can offer the tree little energy for the next year. Since the final leaves of the year are responsible for transfering the energy for the tree to start it out in spring, it seems reasonable to keep the tree as healthy as possible during this last a most crucial part of its season. This means that the tree has to be healthy, not just living.

This is what Boon Manakitivipart has to say about bonsai soil and healthy and living:

“But there is an additional thing about soil and bonsai people. I have found people’s evaluation of soils faulty, because many bonsai people do not make a difference between “alive” and “healthy.” So many think if their trees are not dying, their soil must be a good one. But death or no death is not what you are looking for. A healthy tree has the right amount of bust, the right color. Healthy trees are more flexible than trees that are just able to keep themselves alive. Here is where training is important. Every species may tell you in a different way whether they are healthy or not. Just because it is not dying does not mean that it is healthy.”